A test of the Archaic <i>Homo</i> Introgression Hypothesis for the Chiari malformation type I
Bibliographic record
Abstract
Abstract The Chiari malformation type I (CM-I) is a herniation of the cerebellum through the foramen magnum. Its proximate cause is accepted to be an unusually small occipital bone. However, its ultimate cause remains unclear. In 2013, Fernandes and colleagues hypothesized that individuals develop CM-I because some of their cranial development-coding genes derive from three extinct Homo species that have smaller basicrania than is typical for modern humans—Homo erectus, Homo heidelbergensis, and Homo neanderthalensis. Here, we report a study in which we used 3D data and Geometric Morphometrics to evaluate this hypothesis. We began by investigating whether CM-I is associated with significant differences in cranial shape in a sample of living humans. Subsequently, we compared the crania of living humans with and without CM-I to fossil crania assigned to H. erectus, H. heidelbergenesis, H. neanderthalensis, and H. sapiens. The study’s results were mixed. The first set of analyses identified significant shape differences between the crania of people with CM-I and the crania of unaffected people, which is in line with the hypothesis. In contrast, the second set of analyses did not support the hypothesis. They indicated that the crania of living humans with CM-I are only closer in shape to one of the extinct species, H. neanderthalensis. The other two extinct species were found to be closer in shape to living humans without CM-I. This is contrary to the main prediction of the hypothesis. Together, our results suggest the hypothesis should be narrowed to focus on introgressed genes from Neanderthals.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.005 | 0.015 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.004 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.016 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".